The present invention relates generally to gas turbine engines and more particularly to process integration of the gas turbine engines with other process outside the gas turbine engine.
A gas turbine engine typically comprises in serial-flow relationship, an air intake (or inlet), a compressor, a combustor, a turbine, and a gas outlet (or exhaust nozzle). The compressed air at the compressor discharge is typically utilized by a combustor to generate a hot working fluid. The turbine components such as vanes, blades and static parts for example, which are in thermal contact with the hot working fluid experience a significant temperature rise during operation. It is therefore generally desirable to cool such components during operation to avoid thermal stresses generated by elevated temperatures and thermal gradients.
In conventional approaches, cooling is typically accomplished through bleeding a portion of the compressed air from the compressor and channeling the coolant fluid suitably through various local circuits of the turbine. In a conventional gas turbine engine, the coolant fluid stream typically mixes with the working fluid stream inside the turbine and the exhaust is directed to a stack through an exhaust heat recovery unit. Accordingly, the coolant fluid stream cannot be utilized as a process fluid for another process downstream of the turbine. Additionally, fuel requirement of the combustor to maintain a desired operating temperature at the turbine inlet cannot be optimized so as to maintain a desired operating efficiency range of the gas turbine engine. Although in practice some of the optimization may be performed, in general the system may not be fully optimized.
Currently employed techniques include, utilization of a separate recuperating mechanism, so as to preheat the compressed air. However, the increased pressure drop due to the recuperating mechanism has an adverse impact in maintaining thermodynamic efficiency of the gas turbine engine within the desired range.
In certain other techniques, a portion of the fluid compressed by the main compressor of the gas turbine engine, is extracted from a plenum chamber surrounding the combustor and the coolant fluid stream is accordingly channeled through a cooling circuit in the turbine to cool the turbine components. The coolant fluid stream is further channeled through another off board auxiliary compressor and a heat exchanger disposed adjacent to the turbine. Consequently, the coolant fluid stream is returned to the combustor or combustor plenum chamber after cooling the turbine components. Although in general, cooling of the turbine components is performed in a closed circuit manner however in practice, some of the coolant fluid stream may mix with the working fluid stream in the working fluid flow path of the turbine.
Certain other closed-circuit cooling techniques for gas turbine engines extract coolant fluid from any suitable stage of the main compressor. The coolant fluid stream is returned to a suitable injection stage of the main compressor having a lower pressure than the extraction stage so as to drive the coolant fluid through the closed circuit in the turbine without mixing with the working fluid stream. Although the techniques described above may reduce aero-thermodynamic losses of the gas turbine engine to a certain extent, either a portion or entire of the preheated coolant fluid stream cannot be utilized as a process fluid stream for an adjacent system typically outside a control volume of the gas turbine engine.
Accordingly, there is a need in the art of gas turbine engines for an improved technique which can utilize at least a portion of the preheated coolant fluid stream as a process fluid stream for another process, while maintaining overall thermodynamic efficiency of the gas turbine engine.